Oldboy

In 1988, businessman Oh Dae-su is arrested for assault and drunkenness, consequently missing his daughter's fourth birthday. Shortly after being collected by his friend Joo-hwan, Dae-su is abducted. He awakens in a sealed room with a television, from which he learns that he has been framed for his wife's murder. Growing deranged from the solitude as years pass, Dae-su theorizes about the identity of his captor, trains himself in martial arts, creates a hole in the wall with chopsticks to attempt to escape through, and attempts suicide by slitting his wrists (after which he is resuscitated).

In 2003, Dae-su is sedated, hypnotized, and released. He encounters a suicidal man about to jump off a rooftop with his dog. Dae-su relays his story to the man, allowing him to jump upon finishing. Dae-su enters a sushi restaurant and collapses after receiving a call from his captor. The chef, Mi-do, takes him in.

Dae-su and Mi-do attempt to track down Dae-su's daughter, but relent after being informed that she has been adopted by a foreign family. After identifying the restaurant that prepared his prison meals and following a delivery driver, Dae-su locates his former prison, which he discovers is a private facility where people pay to have others incarcerated. He tortures and interrogates the warden, Park, who claims Dae-su was imprisoned for "talking too much." Dae-su escapes after fighting off Park's thugs.

Dae-su's captor, calling himself "Evergreen," sets up a meeting with Dae-su and promises to commit suicide by remotely deactivating his pacemaker if Dae-su uncovers his motive within five days; otherwise, Evergreen will kill Mi-do. Dae-su returns to Mi-do's apartment to find Park and his thugs molesting her. Park prepares to torture Dae-su, but stops when Evergreen sends a briefcase of cash. Dae-su threatens to cut off Park's hand before the latter leaves.

Dae-su and Mi-do gradually grow closer, eventually becoming sexually intimate. Dae-su awakens the following morning to find Park's severed hand in a box. Remembering his high school slogan, "Evergreen Old Boys," he identifies Evergreen as his former schoolmate Lee Woo-jin. He calls Joo-hwan, who recounts that his late classmate Lee Soo-ah—Woo-jin's sister—was a "slut"; an eavesdropping Woo-jin angrily stabs him to death.

After seeking out and consulting Soo-ah's friends, Dae-su recalls having seen Soo-ah and Woo-jin have sex in high school. Unaware that he was witnessing incest, Dae-su casually mentioned the incident to Joo-hwan, who subsequently spread gossip about Soo-ah's promiscuity, culminating in a rumor that she was pregnant and driving her to suicide.

Dae-su confronts Woo-jin at the latter's penthouse. He implicates that Woo-jin killed Soo-ah, fearing the consequences of impregnating her, and shifted the blame to Dae-su to alleviate himself of the guilt. Woo-jin maintains that Soo-ah was merely experiencing phantom pregnancy as a result of the rumors. He then gives Dae-su a photo album, which reveals that Mi-do is Dae-su's daughter, and explains that he orchestrated Dae-su and Mi-do's meeting and relationship via hypnosis. A horrified Dae-su desperately pleads for forgiveness and begs Woo-jin not to tell Mi-do the truth; when Woo-jin is unmoved, Dae-su cuts out his own tongue as penance. Woo-jin finally agrees not to contact Mi-do and gives Dae-su the pacemaker remote. When Dae-su tries to use it, it only plays a recording of his tryst with Mi-do, making him collapse in despair. In the elevator, Woo-jin smiles smugly, but begins to hallucinate his sister's suicide. Realizing his vengeance has fixed nothing, a distraught Woo-jin fatally shoots himself in the head.

Dae-su locates the hypnotist and asks her to erase his knowledge of Mi-do being his daughter. Touched by a specific line in his letter—"Even though I'm no better than a beast, don't I have the right to live too?"—she guides him to envision the part of himself that knows the truth dying. Mi-do finds Dae-su lying alone in the snow and professes her love for him. The two embrace while Dae-su smiles, which soon turns into a tortured grimace.